Electrical impedance of white spruce shoots in relation to pressure-volume analysis and free sugar content

Electrical impedance measurements made on white spruce, Picea glauca (Moench) Voss, stems were related to shoot free sugar contents and to osmotic, turgor and water potential. During seasonal dormancy induction, there were commensurate increases in free sugar contents, osmotic potential at full turgor and impedance which resulted in linear relationships among these variables. When measured over the course of laboratory drying, impedance increased curvilinearly with decreasing relative water content. There was a linear increase in impedance with decreasing water potential, with a break point coincident with the turgor loss point, possibly attributed to disruption to current flow through broken plasmodesmatal connections between adjacent cells. This technique offers a non-destructive method to measure tissue free sugar content, and therefore, short- and long-term shifts in parameters historically derived from pressure-volume analysis.     

Critical role of mitochondrial dysfunction and impaired mitophagy in diabetic nephropathy

Mitochondrial dynamics play a critical role in deciding the fate of a cell under normal and diseased condition. Recent surge of studies indicate their regulatory role in meeting energy demands in renal cells making them critical entities in the progression of diabetic nephropathy. Diabetes is remarkably associated with abnormal fuel metabolism, a basis for free radical generation, which if left unchecked may devastate the mitochondria structurally and functionally. Impaired mitochondrial function and their aberrant accumulation have been known to be involved in the manifestation of diabetic nephropathy, indicating perturbed balance of mitochondrial dynamics, and mitochondrial turnover. Mitochondrial dynamics emphasize the critical role of mitochondrial fission proteins such as mitochondrial fission 1, dynamin-related protein 1 and mitochondrial fission factor and fusion proteins including mitofusin-1, mitofusin-2 and optic atrophy 1. Clearance of dysfunctional mitochondria is aided by translocation of autophagy machinery to the impaired mitochondria and subsequent activation of mitophagy regulating proteins PTEN-induced putative kinase 1 and Parkin, for which mitochondrial fission is a prior event. In this review, we discuss recent progression in our understanding of the molecular mechanisms targeting reactive oxygen species mediated alterations in mitochondrial energetics, mitophagy related disorders, impaired glucose transport, tubular atrophy, and renal cell death. The molecular cross talks linking autophagy and renoprotection through an intervention of 5′-AMP-activated protein kinase, mammalian target of rapamycin, and SIRT1 factors are also highlighted here, as in-depth exploration of these pathways may help in deriving therapeutic strategies for managing diabetes provoked end-stage renal disease.     

Nitrate induced iron deficiency chlorosis in Juncus acutiflorus

Chlorosis caused by iron deficiency is commonly associated with high bicarbonate levels in the soil. However, in rare cases such chlorosis has been observed in soils with high nitrate levels. In a dutch rich-fen, chlorosis has been noted in stands of Juncus acutiflorus at locations where groundwater containing high levels of nitrate reached the surface. Experiments revealed that the chlorosis could be attributed to iron deficiency although iron levels in the shoots were well above the known physiological threshold values for iron deficiency. It is postulated that increased nitrate assimilation leads to an increased apoplastic pH and to a concomitant immobilisation of iron and/or lower iron (III) reduction. Moreover free amino acid levels were markedly higher in the iron deficient plants in the field. It was found, however, that the percentage of nitrogen present as free amino acids was not influenced directly by low iron levels but mainly by the C/N ratios in the shoots. Nowadays, nitrate concentrations in ground water as high 1000 µM are no longer an exception in the Netherlands. We propose that strongly increased nitrate inputs may cause iron stress in natural vegetations, especially in wet habitats.     

Apoptosis induction with electric pulses — A new approach to cancer therapy with drug free

Electrical pulses have been widely used in biomedical fields, whose applications depend on the parameters such as durations and electric intensity. Conventional electroporation (0.1-1 kV/cm, 100 μs) has been used in cell fusion, transfection and electrochemotherapy. Recent studies with high-intensity (MV/cm) electric field applications with durations of several tens of nanoseconds can affect intracellular signal transduction and intracellular structures with plasma intact, resulting in an application of intracellular manipulation. The most recent development is the finding that parameters between those two ranges could be used to induce apoptosis of cancer cells. Proposal of apoptosis induction and tumor inhibition has advantages to pursue the treatment of cancer free of cytotoxic drugs.     

Pyrroline-5-carboxylate reductase from Cucurbita cotyledons

Pyrroline-5-carboxylate reductase, which required reduced pyridine nucleotide and Δ′-pyrroline-5-carboxylate for proline synthesis, was isolated from pumpkin cotyledons. The enzyme was found in the soluble fraction and had a 4.5-fold greater activity with NADH than NADPH. The enzyme was inhibited by NH₂OH, NADP, ATP and slightly by proline. Glutathione or pyridoxal-5-phosphate had little effect on enzyme activity. The enzyme had a pH optimum between 7·0 and 7·6 and was not inhibited by high concentrations of NADH or Δ′-pyrroline-5-carboxylate.     

Electrochemical Characteristics of Nitro-Heterocyclic Compounds of Biological Interest. III. Nitroso Derivative Formation

Upon electrolytic reduction of a range of nitro-aromatic complexes (including imidazoles. benzenoids. furans and pyrazoles) an associated oxidation-reduction process is observed at more positive potentials with respect to nitro group reduction when using repeat scan cyclic voltammetry. This new couple has been identified as the reversible first reduction of the nitroso derivative for chloramphenicol, by the addition of a genuine sample of nitrosochloramphenicol to the electrochemical cell. We have failed to observe formation of the new redox-active species for five 5–nitroimidazoles examined.

Possible reaction schemes for nitroso formation under electrolytic reduction conditions and the importance of the nitroso redox couple with respect to the cytotoxic action of the parent drug are discussed. The applicability of nitrosochloramphenicol as a model for the behaviour of nitroso-heterocycles in general is shown.     

Mobile Communication in the Public Mind: Insights from Free Associations Related to Mobile Phone Base Stations

The number of people using mobile phones has dramatically increased. At the same time, many people are unsettled about the potential health effects from the electromagnetic fields generated by mobile phone base stations. Research indicates that the risks associated with base stations are perceived differently by experts, laypeople, and base station opponents. Using a free association method, we analyzed these differences in more detail. In our first study, we found no difference between experts and laypeople but a marked distinction in the associations of opponents as opposed to the first two groups. The prevalence of free associations in a large random sample from the general population was explored via correspondence analysis in the second study. People who assign high risks to mobile communication had different, more negative associations in mind (e.g., “senselessness,” “hazard”) compared to people with low risk-perception (e.g., “mast,” “acceptance”). Our research is in line with the assumption that the affect heuristic guides risk and benefit assessments, and highlights the role of affect in risk perception and communication.     

Free radical mechanisms in enzyme reactions

Free radicals are formed in prosthetic groups or amino acid residues of certain enzymes. These free radicals are closely related to the activation process in enzyme catalysis, but their formation does not always result in the formation of substrate free radicals as a product of the enzyme reactions. The role of free radicals in enzyme catalysis is discussed.